Receivers for the reception of electromagnetic waves of any desired frequency



Jan. 21, 1964 D. EIGEN ETAL 3,119,066

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a W ATTORNEY United States Patent RECEHVEFS Filth THE RECEPTIGN 0FELECTRQ- MAGNETEC WAVES 0F ANY DEdlRED FRE- QUENCY David Eigen, Passaic,and Albert W. Peer, Kinnelon, NIL, assignors to The Olronite Company,Passaic, N.J., a corporation of Delaware Original appiication Mar. 16,1959, Ser. No. 799,791, new Patent No. 3,032,652, dated May 1, 1962.Divided and this application Feb. 5, 1962, Ser. No. 171,118

6 Claims. (Cl. 325-476) Our invention relates to receivers for thereception of electromagnetic impulses of any frequency. Receivers ofthis general type are commonly used in the reception ofamplitude-modulated radio, television, and similar signals transmittedthrough the atmosphere or through space outside the atmosphere from asource relatively remote from the receiving apparatus.

Existing apparatus for the reception of such signals,

hereinafter referred to as desired signals, also pick up undesiredelectromagnetic impulses, hereinafter referred to as noise. If the ratioof the strength of pickup of the desired signal to the strength ofpickup of noise is high, the desired signal can be clearly recorded,displayed, heard, seen, or otherwise made to be understood, or can beused faultlessly, when sufficiently amplified, rectified, and fed intothe proper transducer, to operate control ..echanisms. Such a signal issaid to be of high quality. On the other hand, if the ratio of thedesired signal to noise is low, amplification does not increase theclarity of the desired signal in that, when the desired signal isamplified, the noise is also amplified in an equal ratio. Under theseconditions, understanding of the desired signal is difiicult orimpossible, and when such deserved signals are used to operate controlor metering mechanisms, they often give faulty operations. Such signalsare said to be of low quality.

An object of our invention is to provide means whereby the effects ofnoise emanating from without the receiver will be substantiallycancelled before reaching the transducer, thus leaving a clear,high-quality desired signal for operating the transducer.

A further object of our invention is to provide means within thereceiver whereby a high ratio of desired signal to noise from alow-quality signal pickup is attained, thereby permitting greatamplification while attaining high quality of the desired signal foractuation of the transducer.

A further characteristic inherent in our receiver is its abilitysatisfactorily to receive weak signals, even under conditions wherenoise signals are predominant, thereby permitting greater distance ofsignal transmission with the same power.

A still further object of our invention is to provide a receivingapparatus which will permit satisfactory communications even whenatmospheric noise conditions are so severe as otherwise to render thetransmission ineffective.

Another object of our invention is to provide a receiver which willgreatly increase reliability of operation of metering and controlmechanisms and other intelligence transmission apparatus for spacemissiles and space expforation devices and permit the use of lower-powerand, hence, lighter-weight transmitters in such devices.

In the accompanying drawings,

FIG. 1, which includes a typical wiring diagram of a simplifiedsuperheterodyne circuit, illustrates one embodiment of our invention;and

FIGS. 2, 3, 4, and are diagrammatic showings of further embodiments ofour invention as applied to the showing in FIG. 1.

In the superheterodyne principle of reception the modulated carrier waveof the desired signal is first changed "ice into a predeterminedintermediate frequency; then the desired signal at this predeterminedintermediate frequency is amplified, rectified, and transduced, or itmay be further amplified after rectification and then transduced.

In the United States and elsewhere there are frequencies on which thereis no broadcasting, and under the supcrheterodyne principle of receptionthe carrier wave of the desired signal is changed to an intermediatefrequency, which may be chosen to be one of these broadcastfreefrequencies. In conventional superheterodyne radio receivers the carrierwave of the desired broadcast signalis converted into 455 kc., forexample, and the converted signal is then amplified and detected.Television and other communication media similarly use otherintermediate-frequency bands.

One advantage of the superheterodyne principle is that the amplifiers ofa superheterodyne receiver can be permanently adjusted to respond to anintermediate frequen cy so as to amplify, at this single frequency, adesired signal which is being broadcast at any one of the many differentbroadcast frequencies. Such amplification is accomplished without thevarious amplification stages of the receiver having to be adjusted tochange reception from one broadcast frequency to another. The one tuningknob of a superheterodyne receiver controls the tuning circuit of thereceiver to respond to the frequency of the desired modulated sine wavecarrier signal. This knob also simultaneously controls a localoscillator, which is in continual oscillation at a frequency of 455 kc.,for example, either above or below the frequency to which the tuningcircuit is adjusted to respond. The modulated signal from the tuningcircuit and the oscillation signal from the local oscillator are bothfed into a mixer tube, where the modulated sine waves of the desiredsignal and the unmodulated sine wave from the oscillator are mixed.These two frequencies, as well as frequencies representing the sum ofand the difference in frequency of the two signals appear at the plateof the'mixer. The following stages of amplification are all tuned to 455kc., for exam pie, or other intermediate frequency, so that thisfrequency is accepted by the equipment, amplified, detected, and used toactuate the transducing means. All other frequencies cause no responsein the intermediate-frequency part of the circuit and can be said to berejected.

While the superheterodyne receiver was a big step forward in receptionof electromagnetic waves, even such a receiver picks up noise impulses,as above explained, which are mixed with and undesirably furtheramplitude modulate the frequency leaving the tuning circuit. Thisundesirable modulation is carried through the mixer tube into theintermediate-frequency components of the receiver and often obscures thedesired signals reaching the transducer.

We have found that. these various undesired electromagnetic impulses areof a very random nature and contain energy components which will shock aresonant circuit into oscillation, even though the resonant circuit maybe tuned to only a specific single frequency. We have found also thatoscillation can be initiated with approximately equal vigor by the samenoise impulse and can be made to decay at the same rate, even thougheach of two separate resonant circuits may be tuned to specificfrequencies widely spaced from each other.

Our invention utilizes these findings to neutralize the undesirable partof the modulation of the desired signal by providing theintermediate-frequency components of the receiver with a second paththrough which the noise impulses may be introduced to cause modulationof the desired signal, in opposition to modulation caused by noiseimpulses entering the receiver through the normal path. This second pathcontains means to provide degree phase displacement from the normalpath. The second-path noise impulse modulations being 180 degreesphase-displaced from and of approximately the same vigor as thenormal-path noise impulse modulations, the noise impulse modulationsentering the receiver via one path and those entering the receiver viathe other path neutralize each other, leaving a correctly modulateddesired signal.

Referring to the drawings in detail,

FIG. 1 shows a schematic wiring diagram of a superheterodyne circuit asmodified by our invention, 2 designating the antenna and 4 the antennalead. For simplicity and clarity, the tuning circuit, the localoscillator, the mixer circuit including the mixer tube, and theintermediate-frequency components have been enclosed in dotted lines anddesignated 6, 8, 1i), and 12, respectively. The other elements of thereceiver, such as detector, audio amplifier, transducer, and powersupply are shown by typical conventional symbols but not furtheridentified, as they are widely understood by those skilled in this art.

In this embodiment of our invention we have provided one of the elementsof the intermediate-frequency components 12, viz, transformer 14, withtwo identical and closely coupled, preferably bifilar wound, primarywindings 16 and 18. 20 designates the usual secondary winding of thetransformer, this winding being conventionally coupled to the primarywindings. One end of the primary winding 16, as seen in FIG. 1, isconnected to the plate of a mixer tube 17 and its opposite end tojunction 22, to which is also connected the source of plate supplyvoltage and A.-C. ground, as shown. One end of the other primary winding18 of the transformer 14 is connected to lead 4 of the antenna 2 bymeans of a lead 24, while the opposite end of the primary winding isconnected to the junction 22. An isolating capacitor 23 is inserted inthe lead 24 between primary winding 13 and the junction of lead 24 withantenna lead 4.

As will be seen from the drawing, the connection of primary winding 16to the plate of mixer tube 17 and the connection of primary winding 18to the antenna lead 4 are so chosen that an impulse entering primarywinding 16 at that end which is connected to the plate of the mixer tube17 and proceeding through the winding to the junction 22, and the sameimpulse entering winding 18 at that end which is connected to theantenna lead 4 and proceeding through the winding to the junction 22will tend to set up magnetic fields of opposite polarity in thetransformer 14; therefore, identical and in-phase impulsessimultaneously entering primary winding 16 and primary winding 18 willexactly cancel each other, so that no electrical impulse therefrom willbe imposed on the secondary winding 20 of the transformer.

It will be appreciated that the desired signal enters the receiverthrough the antenna 2 and proceeds through antenna lead 4 and the tuningcircuit 6, which includes tuning coil 5, and, as explained earlier,there are undesired amplitude modulations of the tuned waves of energyleaving the tuning circuit due to noise impulses. The desired modulatedsignal with the additional undesired modulation just mentioned is mixedin the mixer circuit with the frequency emanating from the localoscillator 8.

As previously pointed out, the transformer 14 and its associatedintermediate-frequency components 12 accept only the predeterminedintermediate frequency, the other frequencies emanating from the mixercircuit causing no response in the intermediate-frequency components 12.It will be appreciated, therefore, that our invention distinguishes fromconventional receivers, where the transformer 14 has only one primarywinding, and the responses in the intermediate-frequency components 12are undesirably amplitude-modulated by the noise impulses transmitted tothe components 12 through the mixer circuit 10, tuning circuit 6,antenna lead 4, and antenna 2.

To overcome the undesirable part of the modulation of the 455 kc. orother broadcast-free frequency, we provide the transformer 14 with theadditional primary winding 18, connected as above explained, throughwhich the noise impulse at the random frequency is introduced into thetransformer.

Since there are no broadcasts at the selected inter mediate frequency,it will be appreciated that only those components of the noise impulseswhich will shock the selected intermediate-frequency resonant circuitinto oscillation will be accepted and cause response in theintermediate-frequency components 12. However, any such response is inphase opposition to the response of components 12 caused by the sameimpulse entering the primary winding 16. Therefore, the resultantresponses of components 12 are due only to the mismatch of phase angleand intensity of such impulses entering the transformer 14 through thetwo primary windings.

.e have found that with simple circuits the lead 24 can be generallyconnected directly from the winding 18 to the antenna lead 4 through theisolating capacitor 23, so that with a properly constructed transformer14 the mismatch of phase angle or intensity of impulses due to noise isso slight as to be negligible, practically all noise being cancelled.

However, to provide for applications of the cancellation of signal incircuits where the above arrangement would not be adequate, or toprovide finer adjustment of the cancellation, or to compensate fortransformer inaccuracies, we may employ a phase-shifter 26 (see FIG. 2)in the lead 24 to adjust electrical constants of the lead 24, so thatthe phase angle and intensity of the 455 kc. or otherintermediate-frequency components of the noise impulse reaching thetransformer secondary winding 20 through the primary winding 18 will beof exact proportion to cancel that reaching secondary winding 20 throughprimary winding 16. The phase-shifter 26 may take many forms, all ofwhich are contemplated. In the form illustrated in FIG. 2 we provide aninductance 28, shunted by a resistor 30. The inductance 28 may be fixedand the resistor adjustable, as shown, or vice versa. In thephase-shifter illustrated in FIG. 3 we provide a condenser 32, shuntedby a resistor 39. The condenser may be fixed and the resistoradjustable, as shown, or vice versa. Any of these arrangements, it willbe appreciated, permit adjustment of phase angle and intensity of theimpulses flowing along the lead 24 to the transformer 14.

In those applications of our principle to circuits where the variousadjustments of the tuning circuit to select broadcast signals ofdifferent frequencies cause intoler' able interaction between the tuningcircuit 6 and the transformer 14 along the antenna lead 4 and the lead24, said interaction can be eliminated by the arrangement shown in FIG.4, wherein the lead 4 of antenna 2 is oniy connected to the tuning coil5 and we provide an antenna 34 in addition to the conventional antenna2. This additional antenna 34 is connected by lead 25 to the primarywinding 18 of the transformer 14. It is important that the antenna 2 andantenna 34 be similarly oriented in order that they similarly respond tonoise impulses originating from the same direction. -It is notnecessary, however, that the two antennas be the same in size, asamplification or attenuation can be accomplished within the receiver bythe means indicated herein or by other well known means. A slightphysical separation of the two antennas efiectively decouples theantennas and thereby prevents interaction between the tuning circuit 6and transformer 14 along the antenna lead 4 and lead 24. Alternatively,as shown in FIG. 5, this interaction can be adequately prevented byplacing a decoupling impedance 36 in the antenna lead 4 between thetuning circuit 6 and the junction of lead 24 with antenna lead 4. Thisdecoupling impedance 36 can be a resistance or an inductance or acapacitance or a combination of these elements, as convenience oreconomy dictates.

It is to be understood that the use of the phase-shifter 26 is not to beconfined to the single-antenna arrangement illustrated, but it can beused in conjunction with the dual-antenna arrangement shown in FIG. 4.It is also to be understood that both the phase-shifter 26 and thedecoupling impedance 36 may be used in connection with a single antennain the practice of our invention.

From the foregoing it will be appreciated that we have provided means tosupply intermediate-frequency oscillations which are amplitude-modulatedonly by the desired signal and are free of all undesired modulations.When these modulated oscillations are further amplified, detected, andtransduced, a clear, clean, high-quality response of the transducer canbe attained, regardless of severity of the noise signals in theatmosphere or in the vicinity. The transducing means may, of course, beany of the conventional visual, audio, or recording devices, or may be amechanical device for initiating action, for example a valve closer, camadjuster, or plunger actuator, etc.

As can be noted from FIG. 1, circuits in accordance with our inventionrequire only one knob to tune the set.

While we have shown the opposing noise signal introduced at the firstintermediate-frequency stage, it will be appreciated that the opposingnoise signal may be introduced, prior to detection, at any desired laterstage of amplification. However, such later introduction complicates tosome extent the exactness of equipment required for perfect cancellingof unwanted noise. Then, too, the introduction of the opposing noisesignal at the earliest possible position keeps to a minimum theadditional equipment required. Introduction of the opposing noise signalat the earliest possible position makes unnecessary the uselessamplifying of undesired signals, thereby reducing load on succeedingamplifiers and other components and/or permitting greater output of thedesired signal per stage of amplification.

It is common practice in more intricate superheterodyne circuits to useone or more stages of pre-amplification before conversion to theintermediate frequency. In such receivers we contemplate that suitablepre-amplification will also be introduced into the lead 24.

It is to be understood that, while the transformer 14 has been shownwith the secondary winding 20, this winding may be eliminated byconnecting the two leads of this secondary to the ends of primarywindings 16 and 18.

As above noted, our receiver is usable for radio, television,telemetering, or other intelligence, or remotecontrol applications wherethe signal must be transmitted through air or through space outside theatmosphere, and since weak signals can be satisfactorily separated fromhigh levels of noise impulses, it will be appreciated that, on receiverswithin space missiles and other devices, the receivers will correctlyactuate the control devices from ground signals which would nototherwise be of satisfactory quality. Conversely, the transmitterscarried by such devices can be of smaller power and lighter weight ifour receiver is employed on the ground to receive signals from themissiles.

It is to be understood that changes may be made in the details ofconstruction and arrangement of parts hereinabove disclosed within thepurview of our invention.

This application is a division of our copending application Serial No.799,791, filed March 16, 1959, now Patent No. 3,032,652, Receivers forthe Reception of Electromagnetic Waves of Any Desired Frequency.

What we claim is: i

1. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; and an interstage tuned to anintermediate frequency, including a transformer having two primarywindings; said local oscillator and said tuning coil being connected tothe input of said mixer tube; said tuning coil and one end of onewinding of the said transformer being connected to an antenna for thereceiver; one end of the other primary winding of the transformer beingconnected to the plate of the mixer tube of the mixer circuit; the otherends of the two transformer primary windings having a common junction;the connections of the transformer windings being so chosen that theonly electrical impulses affecting the secondary of the transformer arethose impulses of said intermediate frequency appearing in thesecond-mentioned primary winding modified by those impulses of saidintermediate frequency appearing in the first-mentioned primary winding.

2. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; an interstage, tuned to anintermediate frequency, including a transformer having two primarywindings, said local oscillator and said tuning coil being connected tothe input of said mixer tube; an antenna to which said tuning coil andone end of one winding of the said transformer are connected, one end ofthe other primary winding of the transformer being connected to theplate of the said mixer tube, the other ends of the two transformerprimary windings having a common junction, the connections of thetransformer windings being such that the only electrical impulsesaffecting the secondary of the transformer are those impulses of saidintermediate frequency appearing in the second-mentioned primarywinding, modified by those impulses of said intermediate frequencyappearing in the first-mentioned primary winding; and an adujstablephase-shifter in the lead connecting one end of said transformer to saidantenna.

3. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; an interstage, tuned to anintermediate frequency, including a transformer having two primarywindings, said local oscillator and said tuning coil being connected tothe input of said mixer tube; an antenna to which said tuning coil andone end of one winding of the said transformer are connected, one end ofthe other primary winding of the transformer being connected to theplate of the said mixer tube, the other ends of the two transformerprimary windings having a common junction, the connections of thetransformer windings being such that the only electrical impulsesaffecting the secondary of the transformer are those impulses of saidintermediate frequency appearing in the second-mentioned primarywinding, modified by those impulses of said intermediate frequencyappearing in the first-mentioned primary winding; and a phase-shifter inthe lead connecting one end of said transformer winding to said antenna,said phase-shifter comprising an inductance shunted by a resistor, oneof said elements of the phase-shifter being adjustable.

4. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; an interstage, tuned to anintermediate frequency, including a transformer having two primarywindings, said local oscillator and said tuning coil being connected tothe input of said mixer tube; an antenna to which said tuning coil andone end of one winding of the said transformer are connected, one end ofthe other primary winding of the transformer being connected to theplate of the said mixer tube, the other ends of the two transformerprimary windings having a common junction, the connections of thetransformer windings being such that the only electrical impulsesaffecting the secondary of the transformer are those impulses of saidintermediate frequency appearing in the second-mentioned primarywinding, modified by those impulses of said intermediate frequencyappearing in the first-mentioned primary winding; and a phase-shifter inthe lead connecting one end of said transformer winding to said antenna,said phase-shifter comprising a condenser shunted by a resistor, one ofsaid elements of the phase-shifter being adjustable.

5. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; an interstage, tuned to anintermediate frequency, including a transformer having two primarywindings, said local oscillator and said tuning coil being connected tothe input of said mixer tube; an antenna connected to said tuning coil;a second antenna oriented similarly to the first-mentioned antenna, saidsecondmentioned antenna being connected to one end of one winding ofsaid transformer, one end of the other winding of the trasformer beingconnected to the plate of the mixer tube, the other ends of the twotransformer primary windings having a common junction, the connectionsof the transformer windings being such that the only electrical impulsesaffecting the secondary of the transformer are those impulses of saidintermediate frequency appearing in the second-mentioned primarywinding, modified by those impulses of said intermediate frequencyappearing in the first-mentioned primary winding.

6. A receiver for the reception of electromagnetic waves of any desiredfrequency, said receiver comprising a tuning coil; a local oscillator; amixer circuit, including a mixer tube; an interstage, tuned to anintermediate frequency, including a transformer having two primarywindings, said local oscillator and said tuning coil being connected tothe input of said mixer tube; an antenna to which said tuning coil andone end of one winding of the said transformer are connected; and adecoupling impedance in the lead connecting the antenna to the tuningcoil, one end of the other primary winding of the transformer beingconnected to the plate of the said mixer tube, the other ends of the twotransformer primary windings having a common junction, the connectionsof the transformer windings being such that the only electrical impulsesatfecting the secondary of the transformer are those impulses of saidintermediate frequency appearing in the second-mentioned primarywinding, modified by those impulses of said intermediate frequencyappearing in the first-mentioned primary winding.

References Cited in the file of this patent UNITED STATES PATENTS1,590,635 McCaa June 29, 1926 2,000,142 Loewenstein May 7, 19352,101,529 Breedlove Dec. 7, 1937 2,227,415 Woltf Dec. 31, 1940 2,791,686Lambert May 7, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No, 3, 119,066 January 21, 1964 David Eigen et a1 Itis hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the grant, line 1 and in the heading to the printed specification,line 5, name of inventor for "Albert W; Peer I each occurrence, readRobert W, Peer column 1, line 33, for "deserved" read desired Signed andsealed this 7th day of July 1964,

(SEAL) Attest:

ERNEST W; SWIDER EDWARD J. BRENNER Arresting Officer Commissioner ofPatents

1. A RECEIVER FOR THE RECEPTION OF ELECTROMAGNETIC WAVES OF ANY DESIREDFREQUENCY, SAID RECEIVER COMPRISING A TUNING COIL; A LOCAL OSCILLATOR; AMIXER CIRCUIT, INCLUDING A MIXER TUBE; AND AN INTERSTAGE TUNED TO ANINTERMEDIATE FREQUENCY, INCLUDING A TRANSFORMER HAVING TWO PRIMARYWINDINGS; SAID LOCAL OSCILLATOR AND SAID TUNING COIL BEING CONNECTED TOTHE INPUT OF SAID MIXER TUBE; SAID TUNING COIL AND ONE END OF ONEWINDING OF THE SAID TRANSFORMER BEING CONNECTED TO AN ANTENNA FOR THERECEIVER; ONE END OF THE OTHER PRIMARY WINDING OF THE TRANSFORMER BEINGCONNECTED TO THE PLATE OF THE MIXER TUBE OF THE MIXER CIRCUIT; THE OTHERENDS OF THE TWO TRANSFORMER PRIMARY WINDINGS HAVING A COMMON JUNCTION;THE CONNECTIONS OF THE TRANSFORMER WINDINGS BEING SO CHOSEN THAT THEONLY ELECTRICAL IMPULSES AFFECTING THE SECONDARY OF THE TRANSFORMER ARETHOSE IMPULSES OF SAID INTERMEDIATE FREQUENCY APPEARING IN THESECOND-MENTIONED PRIMARY WINDING MODIFIED BY THOSE IMPULSES OF SAIDINTERMEDIATE FREQUENCY APPEARING IN THE FIRST-MENTIONED PRIMARY WINDING.